\begin{tikzpicture}
    \pgfmathsetmacro{\R}{1.5}

    \tkzDefPoints{0/0/O}
    \tkzDefPoint(170:\R){A}
    \tkzDefPoint(110:\R){C}
    \tkzDefPoint(50:\R){B}
    \tkzDefMidPoint(O,A)  \tkzGetPoint{D}
    \tkzDefMidPoint(O,B)  \tkzGetPoint{E}

    \tkzDrawCircle[thick](O,A)
    \tkzDrawSegments(O,A  O,B  C,D  C,E)

    \tkzLabelPoints[below](O)
    \tkzAutoLabelPoints[center=O, centered, dist= .2](A,B,C)
    \tkzLabelPoints[below](D)
    \tkzLabelPoints[right](E)
\end{tikzpicture}

